1. Field of the Invention
This invention relates to a filtration system. More particularly this invention relates to a filter which is located in a settling tank containing contaminated liquid to be filtered. Contaminants are removed from the liquid by the liquid passing through the filter, and the contaminants are removed from the tank by a continuous conveyor. Such systems are used for continuously filtering liquids such as cutting, cooling and lubricating liquids used in conjunction with machine tools. Metal chips and particles of various sizes and shapes are removed from the liquid.
Even more particularly, this invention relates to a filtration system in which the filter is independent of the conveying system. The contaminants are removed from the filtering surface in the form of vacuum compressed filter cake which is deposited on the conveyor for removal from the settling tank.
2. The State of the Art
There is a wide variety of tank filters used for separating solid metal particles from metal working fluids. A popular system uses a disposable rolled paper filter media which is carried through the tank by a continuous conveyor over a vacuum box which draws the liquid through the media depositing the contaminants on the media. The conveyor is advanced intermittently in synchronism with a vacuum break valve. Paper breaks and infiltration of contaminated liquid around the paper being fed into the tank pose some of the major difficulties with this system.
There is a variety of filters which are not carried by the conveyor but which are operated to continuously or intermittently clean the filtering surface of filter cake which is deposited on the conveyor.
Vertically and horizontally disposed drums are used with the filtering surface being at the periphery of the drum. Removal of filter cake is most commonly performed by doctor blades which scrape the filtering surface as the drum or blades rotate. Other systems use a backwash over a dedicated segment of the drum as it is being rotated. Various difficulties are encountered with the use of these drum filters. For example, with a horizontal drum, an air space tends to build up along the top inside surface which can eventually result in pump cavitation, and the air can also cause literally floating the drum as it is being removed for cleaning or repair. A primary disadvantage of both horizontally and vertically disposed drum filter lies in the difficulty involved in cleaning, repairing and replacing the filtering medium. Even where this medium is a wedgewire screen, which is relatively stiff, it is still fragile and cumbersome to handle as the filtering screen is slid off the drum framework. The drum configuration also limits the filtering area per unit of tank volume occupied.
A recent effort to increase filter area in a metal working system utilizes a pleated filter medium which is flexed by a diaphragm operator and is backwashed with clean liquid.
It is in the area of producing a new filter that can be readily serviced and cleaned and which has a structure that can provide an increased filter area for retrofitting existing tank-conveyor systems or used in a completely new filtration system with the elimination or reduction of prior disadvantages, that the present invention is directed.